Aromatic polyimides containing a dimethylsilane-linked dianhydride

Abstract

A high-temperature stable, optically transparent, low dielectric aromatic polyimide is prepared by chemically combining equimolar quantities of an aromatic dianhydride reactant and an aromatic diamine reactant, which are selected so that one reactant contains at least one Si(CH3)2 group in its molecular structure, and the other reactant contains at least one -CH3 group in its molecular structure. The reactants are chemically combined in a solvent medium to form a solution of a high molecular weight polyamic acid, which is then converted to the corresponding polyimide.

What is claimed as new and desired to be secured by Letters Patent of the United States is: 
     
       1. A high-temperature stable, optically transparent, low dielectric aromatic polyimide prepared by chemically combining equimolar quantities of the aromatic dianhydride bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride ##STR6## with an aromatic diamine containing at least one --CF 3  group in its molecular structure in a solvent medium to form a high molecular weight polyamic acid solution, followed by converting the high molecular weight polyamic acid to the corresponding polyimide. 
     
     
       2. A highly optically transparent and highly insulative aromatic polyimide film prepared from the aromatic polyimide of claim 1 and having a dielectric constant within the range of about 2.5 to 2.8 when measured at 10 GHz. 
     
     
       3. A process for preparing a high-temperature stable, optically transparent, low dielectric aromatic polyimide, which process comprises: (a) providing bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride ##STR7##  as an aromatic dianhydride reactant, and providing an aromatic diamine reactant which contains at least one --CF 3  group in its molecular structure;   (b) chemically combining equimolar quantities of the aromatic dianhydride reactant with the aromatic diamine reactant in a solvent medium to form a high molecular weight polyamic acid solution; and   (c) converting the high molecular weight polyamic acid to the corresponding polyimide.   
     
     
       4. The high-temperature stable, optically transparent, low dielectric aromatic polyimide of claim 2, wherein the aromatic diamine is selected from the group consisting of: 2,2-bis[4(4-aminophenoxy)phenyl]hexafluoropropane,   2,2-bis[4(3-aminophenoxy)phenyl]hexafluoropropane,   2,2-bis(4-aminophenyl)hexafluoropropane, and   3,5-diaminobenzotrifluoride.   
     
     
       5. The process of claim 3, wherein the aromatic diamine is selected from the group consisting of: 2,2-bis[4(4-aminophenoxy)phenyl]hexafluoropropane,   2,2-bis[4(3-aminophenoxy)phenyl]hexafluoropropane,   2,2-bis(4-aminophenyl)hexafluoropropane, and   3,5-diaminobenzotrifluoride.   
     
     
       6. The process of claim 3, wherein the solvent medium is selected from the group consisting of: N,N-dimethylacetamide,   N,N-dimethylformamide,   N-methyl-2-pyrrolidone, and   dimethylsulfoxide.   
     
     
       7. The process of claim 3, wherein the high molecular weight polyamic acid is converted to the corresponding polyimide by thermally treating the high molecular weight polyamic acid in the temperature range of about 250° C. to 300° C. for at least one hour.